Skeptical astrophysicist assesses the fine-tuning argument in Cosmos magazine

Christianity and the progress of science
Christianity and the progress of science

This article appeared in Cosmos Magazine. (H/T Uncommon Descent)

It is written by the naturalist co-author of the new Cambridge University Press book “A Fortunate Universe: Life in a Finely-Tuned Cosmos”.


As a cosmologist, I can use [the] immutable laws of physics to evolve synthetic universes on supercomputers, watching matter flow in the clutches of gravity, pooling into galaxies, and forming stars. Simulations such as these allow me to test ideas about the universe – particularly to try to understand the mystery of dark energy (more on this later).

[…]So now, I invite you to join me in imagining a universe, a universe slightly different to our own. Let’s just play with one number and see what happens: the mass of the down-quark. Currently, it is set to be slightly heavier than the up-quark.

[…]If we start to ratchet up the mass of the down-quark, eventually something drastic takes place. Instead of the proton being the lightest member of the family, a particle made of three up-quarks usurps its position. It’s known as the Δ++. It has only been seen in the rubble of particle colliders and exists only fleetingly before decaying. But in a heavy down-quark universe, it is Δ++that is stable while the proton decays! In this alternative cosmos, the Big Bang generates a sea of Δ++ particles rather than a sea of protons. This might not seem like too much of an issue, except that this usurper carries an electric charge twice that of the proton since each up-quark carries a positive charge of two-thirds.

As a result, the Δ++ holds on to two electrons and so the simplest element behaves not like reactive hydrogen, but inert helium.

This situation is devastating for the possibility of complex life, as in a heavy down-quark universe, the simplest atoms will not join and form molecules. Such a universe is destined to be inert and sterile over its entire history. And how much would we need to increase the down-quark mass to realise such a catastrophe? More than 70 times heavier and there would be no life. While this may not seem too finely tuned, physics suggests that the down-quark could have been many trillions of times heavier. So we are actually left with the question: why does the down-quark appear so light?

Things get worse when we fiddle with forces. Make the strength of gravity stronger or weaker by a factor of 100 or so, and you get universes where stars refuse to shine, or they burn so fast they exhaust their nuclear fuel in a moment. Messing with the strong or weak forces delivers elements that fall apart in the blink of an eye, or are too robust to transmute through radioactive decay into other elements,

Examining the huge number of potential universes, each with their own unique laws of physics, leads to a startling conclusion: most of the universes that result from fiddling with the fundamental constants would lack physical properties needed to support complex life.

Here’s another one a bit later:

And there is another structural issue to consider – our universe is flying apart. Two things affect the rate of expansion: the amount of matter which acts as a brake, and dark energy which acts as an accelerator. Dark energy is winning so our universe is expanding at an accelerating rate.

What this means is that in the early days of the universe, the rate of expansion was slower, slow enough to allow matter to condense into stars, planets and people. But if the universe had been born with only a touch less matter, it would have rapidly expanded, thinning out to less than one hydrogen atom per universe.

On the other hand, if the universe had been born with only a touch more matter, that would have caused it to re-collapse before the first stars could form. In short, the early universe was on a knife-edge, poised between these possible outcomes. What emerged was the Goldilocks expansion rate: not too fast, not too slow.

Later on in the article, the skeptical naturalist astrophysicist evaluates the most popular rebuttal to the scientific evidence: the multiverse.

He concludes:

To some, the picture of the multiverse is comforting, naturally explaining the puzzle of our own fine-tuning. But at present, we have no idea whether this immense sea of universes exists, and they may always be beyond the reach of experiment and observation; if this is the case, is the multiverse more philosophical musing than robust science?

Now, in my experience talking to atheists, especially to the computer science atheists in my office, they simply don’t care that the multiverse cannot be tested or observed. They would rather believe in something that cannot be tested or observed than to go along with the scientific evidence that can be tested and observed. When I try to ask them why they are not interested in conforming their worldview to scientific evidence, they hold up their Star Trek mugs, and their Star Wars DVDs, and say “science will figure it out”. But Star Trek and Star Wars are science fiction, not science – more like fantasy, really.

I have been able to dig down into the worldviews of the naturalists I know who seem to prefer science fiction to science. And at the very core of their worldview I find two things: 1) a desire to dispense with external reality (including science) as a constraint on their seeking of pleasure in this life, and 2) a desire to feel smug about not believing in myths and legends. Unfortunately, I have never met an atheist who did not prefer speculation and fantasy to experimental science, when confronted with scientific evidence that falsifies naturalism. I think that’s a lesson for us all – just because a person is capable at programming a computer (which is good), it doesn’t make a science-fiction / fantasy worldview true.

3 thoughts on “Skeptical astrophysicist assesses the fine-tuning argument in Cosmos magazine”

  1. The fine tuning of the universe never stops to amaze me. I have a question on the multiverse though as to whether it is truly a viable alternative explanation. The multiverse theory assumes some unease generator mechanism that produces universes with slightly different constants and values for fundamental particles. Is there currently a model that explains how that is even possible?

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